A vial or an ampule is used as a container for storing a little amount of drug solution. The vial, mainly a small container made of glass, plastics or the like, is sealed with an opening portion of the container being capped by a rubber stopper. Since it is possible to have a device such as a syringe or the like communicated with the container by inserting a hollow needle through the rubber stopper without breaking (or destroying) the sealing of the container, the operation can be performed hygienically without opening the container imprudently. Therefore, such vial is used as a container for various types of medical agents no matter it is a liquid medical agent or a powder medical agent.
Generally, a vial is produced according to the following procedure. A predefined amount of medical agent is filled into a cylindrical container having an upper portion thereof opened, and a leg portion of the rubber stopper is softly inserted into the opening (half capped). A plurality of such prepared vials are capped in a capper. (In the case of a vial containing a freeze-dried drug product, the vial is put into a freeze dryer at the half capped state to freeze-dry the drug product, and thereafter the vial is capped in a capper.) The capping is performed by lowering a presser plate from the upper side to press the rubber stopper into the vial.
Vials are used and produced as mentioned above; however, use requirements are contradictory to production requirements. In the use, the rubber stopper is pierced through by a hollow needle. If rubber hardness is high, at the time when the hollow needle pierces the rubber stopper, the rubber stopper will be scrapped, resulting in the so-called coring, and it is possible that minute pieces of rubber (impurities) will fall into the vial. Therefore, from the viewpoint of preventing the coring, it is desired to decrease the hardness of the portion to be pierced by the hollow needle.
On the contrary, in the production, the presser plate and the rubber stopper are pressed to contact each other in a capping step. If a top surface of the rubber stopper sticks to the presser plate, at the time when the presser is elevated, the vial will be elevated together with the rubber stopper; as the elevated vial falls down, it may break, which may make the whole lot unusable. Therefore, from the viewpoint of preventing the presser plate and the rubber stopper from sticking to each other, it is desired to increase the hardness of the top surface of the rubber stopper.
In order to offer multiple functions to a rubber stopper, the rubber stopper is formed of multiple rubber materials, such as the one disclosed in Japanese Patent Laying-Open No. 2004-231216. From the viewpoint of keeping medical agents stable for a long term in a vial and preventing the rubber stopper from being degenerated by the medical agents, the vial is entirely formed of chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber or the like; and in order to compensate for resealing capability of a pierced hole which is not possessed by the multiple rubber materials, the portion to be pierced by the needle is formed of natural rubber, isoprene rubber or butadiene rubber.